const Base64 = {

 // private property
 _keyStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",

 // public method for encoding
 encode: function (input) {
     var output = "";
     var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
     var i = 0;

     input = Base64._utf8_encode(input);

     while (i < input.length) {

         chr1 = input.charCodeAt(i++);
         chr2 = input.charCodeAt(i++);
         chr3 = input.charCodeAt(i++);

         enc1 = chr1 >> 2;
         enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
         enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
         enc4 = chr3 & 63;

         if (isNaN(chr2)) {
             enc3 = enc4 = 64;
         } else if (isNaN(chr3)) {
             enc4 = 64;
         }

         output = output +
             this._keyStr.charAt(enc1) + this._keyStr.charAt(enc2) +
             this._keyStr.charAt(enc3) + this._keyStr.charAt(enc4);

     }

     return output;
 },

 // public method for decoding
 decode: function (input) {
     var output = "";
     var chr1, chr2, chr3;
     var enc1, enc2, enc3, enc4;
     var i = 0;

     input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

     while (i < input.length) {

         enc1 = this._keyStr.indexOf(input.charAt(i++));
         enc2 = this._keyStr.indexOf(input.charAt(i++));
         enc3 = this._keyStr.indexOf(input.charAt(i++));
         enc4 = this._keyStr.indexOf(input.charAt(i++));

         chr1 = (enc1 << 2) | (enc2 >> 4);
         chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
         chr3 = ((enc3 & 3) << 6) | enc4;

         output = output + String.fromCharCode(chr1);

         if (enc3 != 64) {
             output = output + String.fromCharCode(chr2);
         }
         if (enc4 != 64) {
             output = output + String.fromCharCode(chr3);
         }

     }

     output = Base64._utf8_decode(output);

     return output;

 },

 // private method for UTF-8 encoding
 _utf8_encode: function (string) {
     string = string.replace(/\r\n/g, "\n");
     var utftext = "";

     for (var n = 0; n < string.length; n++) {

         var c = string.charCodeAt(n);

         if (c < 128) {
             utftext += String.fromCharCode(c);
         } else if ((c > 127) && (c < 2048)) {
             utftext += String.fromCharCode((c >> 6) | 192);
             utftext += String.fromCharCode((c & 63) | 128);
         } else {
             utftext += String.fromCharCode((c >> 12) | 224);
             utftext += String.fromCharCode(((c >> 6) & 63) | 128);
             utftext += String.fromCharCode((c & 63) | 128);
         }

     }

     return utftext;
 },

 // private method for UTF-8 decoding
 _utf8_decode: function (utftext) {
     var string = "";
     var i = 0;
     var c = c1 = c2 = 0;

     while (i < utftext.length) {

         c = utftext.charCodeAt(i);

         if (c < 128) {
             string += String.fromCharCode(c);
             i++;
         } else if ((c > 191) && (c < 224)) {
             c2 = utftext.charCodeAt(i + 1);
             string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
             i += 2;
         } else {
             c2 = utftext.charCodeAt(i + 1);
             c3 = utftext.charCodeAt(i + 2);
             string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
             i += 3;
         }

     }

     return string;
 }
}

module.exports = Base64;